Large Avalanche Turn Outward Problem

  Difficulty: Advanced   Keywords: Joseki, Problem, Question

Jonathan Cano: Here is a problem derived from a variation on the Large Avalanche joseki.

First I present the problem, then the variation on the joseki that gave rise to the problem.

The problem  

Jonathan Cano: White made a mistake in the large avalanche joseki . White reinforces with W1, and then tries to fight it out on the top.

One possible continuation.  

Jonathan Cano:I've looked at some variations that begin with Black a followed by Black b but I don't feel I could play Black here and be certain of killing one of the white+circle and white+square groups ...

A solution? (Black 11 at 'a')  

Andre Engels: After B3, if White plays at W4 here, Black captures the top group. After Black 11, Black clearly has one liberty more.

Does not work either (Black 11 at 'a')  

If instead White plays hane at W4 like here, Black seems to be capturing white stones somewhere, after which the group is dead as well.

Also not interesting  

White might try playing W4 here to live, but even if it works, she needs to add a second stone almost immediately, and the white stones at the right seem to be heading for a fall.

Jonathan Cano: Thanks Andre!

The problem comes from the variation of the large avalanche in which Black plays B1 below.

Large avalanche, Black turns outside  

Jonathan Cano: the normal move for White here is a. In Dictionary of Basic Joseki Ishida Yoshio says W4 at b is a mistake.

A mistake by White  

Jonathan Cano: Ishida says "B2 seems vulgar but it avoids complications and guarantees a favorable result. For his part White has no choice but to make the vulgar ataris of W3 and W5. White answers at a or b."

A mistake by White, continuation b.1  

Jonathan Cano: Here is the continuation when White plays at b in the diagram above.

A mistake by White, continuation b.2  

xela: Years later, KataGo can tell us that W1 here is a mistake. Instead, W1 as a is allegedly sente against the corner (although to be honest, I get lost in the variations and can't see why black needs to reply). After white a, black b, white should sacrifice two stones with W3 at B2, getting a reasonable position. Playing at the marked stone was still a mistake, but only a small one, not the disaster it's painted to be.

A mistake by White, continuation b.3  

Jonathan Cano: After Black 2 Ishida says Black a and b are miai so White is hopeless.

How professionals play  

Checking MasterGo, I found that professionals actually play (4 games out of 4) B1 here rather than at W2 as Ishida proposes. After W4, Black plays either a or b, after which the various groups in the diagram fight things out.

Large Avalanche Turn Outward Problem last edited by xela on June 2, 2024 - 11:02
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